Nitration of hydrocarbon in the presence of trifluoroacetic acid



United States Patent 3,415,868 NITRATION 0F HYDROCARBON IN THE PRES- ENCE 0F TRIFLUOROACETIC ACID Richard D. Smetana, Beacon, and Harry Chafetz, Poughkeepsie, N.Y., assignors to Texaco Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed June 9, 1967, Ser. No. 644,784 4 Claims. (Cl. 260-466) ABSTRACT OF THE DISCLOSURE A method of nitrating alkanes and saturated alicyclic hydrocarbons of between 2 and 50 carbons to produce nitration products comprising contacting said alkanes and alicyclic hydrocarbons in the presence of CF COOH with a nitrating agent selected from the group consisting of N 0 and a P O -HNO -H O combination. The trifluoroacetic acid functions in a catalytic like manner and as a nitration director favoring the production of nitrate derivatives. Further, trifluoroacetate by-products are formed. By standard hydrogenation procedures, the nitrates formed in the resultant nitration product can be converted to their corresponding alkanol and cyclic alcohols and the nitro products therein can be converted to their corresponding alkyl and cyclic amines. The trifluoroacetates can be hydrolyzed to their corresponding alcohols.

BACKGROUND OF INVENTION Field of invention This invention is in the field of art relating to the manufacture of compounds having the general formula:

where R is a monovalent saturated aliphatic radical (alkyl) or monovalent saturated alicyclic hydrocarbyl radical.

Description of the prior art Nitration of alkanes and saturated alicyclic hydrocarbons with dinitrogen pentoxide (N 0 with or without the presence of solvent such as carbon tetrachloride is known. Although these prior N 0 methods produced nitration products, the extent and rate of nitration and the production of nitrates vis-a-vis nitro compounds leave much to be desired. The importance of a nitration reaction favoring the production of nitrates as opposed to nitro derivatives becomes particularly significant if the intended use of the nitration product is the production of alcohols via hydrogenation since nitrates under hydrogenation form alcohols while analogous nitro compounds form amines.

In the method of the present invention the extent and rate of nitration as well as the relative amount of nitrate formation are substantially increased over analogous past procedures.

SUMMARY OF INVENTION This invention relates to a method of preparing nitration products in an improved quantity and rate and having an increased nitrate content. More particularly, our method comprises contacting in the presence of trifluoroacetic acid CF COOH) a member selected from the group consisting of alkane and saturated alicyclic hydrocarbon of from 2 to 50 carbons with dinitrogen pentoxide prepared either outside or in reaction situs via the dehydration of HNO by P 0 or the lower hydrates thereof. We have unexpectedly discovered that trifluoroacetic acid in said method catalytically promotes nitration and selectively directs the reaction to the production of an increased quantity of alkyl and saturated alicyclic hydrocarbyl nitrates at the expense of their nitro counterparts. In addition corresponding hydrocarbyl trifluoroacetate byproducts are formed.

DETAILED DESCRIPTION OF THE INVENTION In the operation of the method of the invention, a hydrocarbon selected from the group consisting of alkanes and saturated alicyclic hydrocarbons of from 2 to 50 carbons is contacted in the presence of CF COOH at a temperature between about 15 and 50 C. and under a pressure between about 1 and atmospheres or higher atmospheres with a nitrating agent selected from the group consisting of N 0 and a combination of P 0 HNO -H O, said combination having a P O /HNO /H O mole ratio between about 1/0.5/0 and 1/ 10/ 1.9, preferably between about 1/1/0 and 1/5/ 1.6. Under advantageous conditions, the mole ratio of CF COOH to hydrocarbon reactant is between about 20:1 and 1:10, preferably between about 10:1 and 1:2, and the mole ratio of HNO to hydrocarbon reactant is advantageously between about 10:1 and 1:10, preferably between about 2:1 and 1:5.

Under the preferred conditions, the reaction is conducted until no more than about 20% of the hydrocarbon is converted into derivative products since substantially higher conversions result in the material formation of undesired ketones, carboxylic acids and polyfunctional compounds. Further, the reaction is preferably conducted under conditions of agitation to facilitate contact of the reactants and at temperatures of between about 0 and 30 C. Agitation of the reaction mixture has been found to promote formation of the hydrocarbyl nitrates and temperatures above about 30 C. tend to favor the production of the nitro compound at the expense of the desired nitrate compounds. Further, at temperatures below about 0 C. the rate of reaction is substantially reduced.

The nitration products are recovered by standard means such as removing the volatile reaction ingredients and byproducts such as NO HNO' and CF COOH via distillation leaving a two-layer residue. The upper layer of said residue comprises the organic nitration products and unreacted paraffin and the lower layer phosphorus acid by-product. The two layers may then be separated by gravity separation and, if desired, the nitration product sent onward to a standard hydrogenation treatment, e.g., utilizing hydrogen and standard hydrogenation catalyst such as a palladium-charcoal-potassium carbonate combine at between about 20 and 100 C. to convert the nitrates into alcohols and the nitro compounds, if any, into the corresponding amines. The remaining triflnoroacetate by-product can be hydrolyzed by standard means to alcohol if desired.

In an alternative method of recovery the nitration products may be separated from the reaction mixture and one another by selective extraction and/or fractional distillation. For example, under mixing conditions subsequent to nitration the reaction mixture is poured into ice water and the resultant aqueous and organic layers are separated from one another and the organic layer is subjected to fractional distillation. Alternatively, the nitration mixture may be poured into a mixture of water and organic selective solvent such as ethyl ether or chloroform under conditions of agitation and after a period of agitation, separating the organic layer from the aqueous layer and subjecting the organic layer to fractional distillation to recover the desired nitrate and nitro compounds as well as trifluoroacetate by-products, if desired.

The nitrating P O -HNO -H O combination as defined represents a mixture of HNO and P or HNO and the lower hydrates of P 0 such as metaphosphoric acid (P O /H O mole ratio=lzl) and polyphosphoric acid (P O /H O mole ratio=1:1.6). The P 0 and hydrates thereof, within the limits defined, function to dehydrate the HNO to N 0 The higher hydrated forms of P 0 outside the scope of the invention, i.e., Where the mole ratio of P O /H O is lower than about 1:19, e.g. pyrophosphoric acid (P O /H O mole ratio=l:2) and orthophosphoric acid (P O /H O mole ratio=lz3), do not significantly dehydrate the HNO and therefore, under the conditions of the invention no significant nitration takes place when said higher hydrated forms are employed as dehydrating agents. Further, the most preferred species of the P O -HNO -H O nitrating agent combination is anhydrous i.e. when the P O /H O ratio is 1/0. As the water content of the nitrating agent combination increases, the combinations eifectiveness decreases. For example, under comparable conditions in the invention method a polyphosphoric acid (P O /H O mole ratio: 1:1.6)-anhydrous nitric acid combination is only 1/20() (i.e., more aqueous) nitric acid, e.g., as low as about 70 wt. percent may be utilized. However, as dilution increases nitration product yield decreases.

Examples of the hydrocarbon reactants contemplated herein are isooctane, dodecane, cyclohexane, methylcyclohexane, methylcyclopentane, and decalin.

Examples of the nitrate and nitro products and trifiuoroacetate by-products contemplated herein are dodecyl nitrates, nitrododecanes, dodecyl trifiuoroacetates, cyclohexyl nitrate, nitrocyclohexane, cyclohexyl trifluoroacetates, methylcyclohexyl nitrates, nitromethylcyclohexanes, methylcyclohexyl trifiuoroacetates, 9 decahydronaphthyl nitrate, 9-nitrodecahydronaphthalene, 9-decahydronaphthyl trifluoroacetate, methylcyclopentyl nitrates, nitromethylcyclopentanes, methylcyclopentyl trifluoroacetates, isooctyl nitrates, nitroisooctanes, and isooctyl trifiuoroacetates.

The following examples further illustrate the method of the invention and are not to be construed as limitations thereof.

EXAMPLE I To a 100 milliliter, 3-necked flask fitted with a condenser, thermometer and stirrer, there was charged in the following order of addition, nitrating agent, trifiuoroacetic acid and hydrocarbon. Vigorous stirring was applied throughout the addition and subsequent reaction. At the end of the reaction period the reaction mixture was poured into a mixture of ml. of ice water and 20 ml. of diethyl ether. The resultant mixture was vigorously shaken. After agitation the aqueous layer of the ,rnixture was separated from the organic layer. The aqueous layer was washed three times with 20 ml. portions of diethyl ether. The resultant organic layers were combined and washed with 70 ml. of ice water and then separated. The organic layer was dried over anhydrous calcium chloride for one hour and the diethyl ether was removed by rotary evaporation at 40C. The organic residue was analyzed utilizing infrared spectrometry and gas chromatography.

The foregoing procedure was employed in five runs utilizing varying ingredients, quantities and reaction conditions. The particular run data and results are reported below in Table I:

TABLE I HNOa/HC React. conditions:

Temp, 5 5 25 25 5 Product yield:

Percent Conversion 1 15. 4 14. 7 16. 2 32. 5 16. 1 Percent Selectivity:

Nitrates 3 68 3 71 8 72 3 74 l 83 Nitroalkanes 6 2 5 9 5 6 5 4 0 Trifluoroacetates 5 25 17 6 19 20 7 17 1 Percent conversion 1 Percent selectivity= moles hydrocarbon consumed moles reactant HO charged moles of particular product X100 moles of reactant HG charged Dodecyl nitrates.

4 Cyclohexyl nitrates.

5 Nitrododecanes.

I Dodecyl trifluoroacetates.

7 cyclohexyl trifluoroacetates. HC=Hydrocarbon.

m.r. =Mole ratio.

as effective as the anhydrous P 0 (P O /H O mole ratio=1:0)-anhydrous nitric acid combination in producing nitration products.

In connection with the above since water associated with the nitric acid employed is included in the water content designation of the combination, the employment of -100% nitric acid is preferred although more dilute EXAMPLE II This example demonstrates the effectiveness of trifluoroacetic acid and nitrating agent as defined in enhancing the extent and rate of nitration and in directing the reaction to the formation of nitrates.

Various runs were employed broadly utilizing the general procedure described in Example I but employing variations in reaction conditions and ingredients to demonstrate the effectiveness of trifluoroacetic acid in enhancing the product yield, reaction rate and selectivity for the formation of nitrates.

The following Table II sets forth test data and results:

TABLE II Run AA BB 00 DD Reactants:

Dodccane. g 7. 7 7. 7 7. 7 7. 7

As can be seen from the foregoing the method of the invention as represented by Run AA has substantially higher conversion rate and nitrate product and acetate by-product yield than comparative Runs BB, CC and DD which respectively employ 1) no catalytic directing solvent (BB), 2) CO1; as a substitute for CF COOH (CC), and 3) B 0 as a dehydrating agent substitute for P205.

We claim:

1. A method of nitrating a member selected from the group consisting of alkane and saturated a'licyclic hydrocarbon of from 2 to carbons, comprising contacting said member in the presence of trifluoroacetic acid with a nitrating agent selected from the group consisting of dinitrogen pentoxide and a P O -HNO -H O combination, said combination having a P O /HNO /H O mole ratio between about 1/0-5/0 and l/ 10/ 1.9 at a temperature between about l5 and 50 C. under a pressure of between about 1 and atmospheres utilizing a mole ratio of trifluoroacetic acid to said member of between about 20:1 and 1:10 and a mole of HNO to said member of between about 10:1 and 1:10.

2. A method in accordance with claim 1 wherein said temperature is between about 0 and 30 C., said nitrating agent is said P O -HNO -H O combination of a mole ratio between l/ 1/ 0 and 1/5/ 1.6, said trifiuoroacetic acid to said member mole ratio is between 10:1 and 1:2 and said HNO to said member mole ratio is between 2:1 and 1:5.

3. A method in accordance with claim 2 wherein said member is dodecane.

4. A method in accordance with claim 2 wherein said member is cyclohexane.

References Cited Titov et al.: Doklady Akad, Nauk SSSR, vol. 81, No. 6, pp. 1085 to 1088 (1951).

LELAND A. SEBASTAN, Primary Examiner.

US. Cl. X.R. 260467, 644, 688 

